as you said ponniyin selvan spurred on an interest in tamil history
but then writers do get carried away sometimes. one classic case is veerapandiya kattabomman.
veerapandiya kattabomman was one who paid his taxes promptly. he had even visited madras as a guest of the british and stayed in the fort st george.
once when he had gone on a holiday it was his minister who sparked off the conflict with the british. anyway kattabommans real name was katta bommu and most of his court dealings were in telugu. so nathu nattayaa kalai pariththaayaa , manjchal araithaaya was a vasanam with remote chances of having ever been spoken.
but talk about kattabomman and we remember this vasanam. so in many if not most places history is often about what a majority wants to hear and not the real truth.
( i think thamil vanan wrote a book called kattabomman kollaikaaran)